Corrosion is a common cause of the deterioration of steel reinforced concrete structures, particularly those exposed to chloride ions from sea water. The hydrated cement present in reinforced concrete is a porous alkaline solid, which usually provides good protection against steel rebar corrosion. In the alkaline pore solution in set cement (pH 12.5-13.5), a protective oxide film is formed over the steel rebar, rendering it passive. However, the rebar corrodes when the protective oxide film is destroyed by chloride or carbonate ions penetrating the concrete. The chloride ions, present in sea water, may penetrate the concrete and raise the pH required to stabilize the passive film to a value which exceeds that of a saturated calcium hydroxide solution. Corrosion of the rebar results under such circumstances. Because the chloride ions penetrate concrete faster than carbonate ions, chloride ion penetration is the primary cause of corrosion in reinforced concrete.
When rebar in reinforced concrete corrodes, the reinforced concrete must be repaired to avoid further deterioration of the rebar and the collapse of the structure that it holds. Rebar also needs protection against such corrosion. For corrosion repair and protection, latexes of one or more of polyvinyl acetate and copolymers of vinyl acetate-ethylene, styrene-butadiene, styrene-acrylic, and acrylic and styrene butadiene rubber emulsions may be mixed with concrete and used. However, a drawback of using such latex based polymer systems is that they may re-emulsify in humid alkaline conditions such as those present in reinforced concrete.